The present invention comprises a new and distinct variety of sweet cherry tree, botanically known as Prunus avium L., and referred to by the varietal name ‘Prim 21’. The new variety was discovered in Baden-Wuerttemberg, Germany as the result of planned breeding between cherry tree variety named ‘PC 7144-7’, known and marketed as “Tieton” (female parent, U.S. Plant Pat. No. 8,051), and an unnamed and unpatented cherry tree variety as the male parent. The purpose of the breeding program was to produce high quality fruits with an early ripening time. The new variety was first asexually reproduced via cuttings in Baden-Wuerttemberg, Germany in 2006. The new variety has been trial and field tested and has been found to retain its distinctive characteristics and remain true to type through successive propagations. The present invention has not been evaluated under all possible environmental conditions. The phenotype may vary with variations in environment without a change in the genotype of the plant.
The new variety is similar to both parental varieties in exhibiting a dark red fruit color, high fruit firmness, and medium early blooming time. The new variety differs from its parental varieties in tree habit, fruit ripening time, and fruit shape. When specifically compared to “Tieton”, ‘Prim 21’ has similar S-alleles/S3S9, but exhibits a medium strong and wide tree habit versus the upright and strong tree habit of “Tieton”, a fruit ripening time that is 8 days earlier than “Tieton”, and fruit that is more heart-shaped than “Tieton”. When compared to cherry tree variety named ‘Burlat’ (unpatented), the fruits of ‘Prim 21’ are more firm and heart-shaped versus the round shape of ‘Burlat’, and ‘Prim 21’ exhibits a weaker growth habit than ‘Burlat’. Further, the following characteristics distinguish the new variety from other varieties known to the breeder:                1. ‘Prim 21’ exhibits a much darker fruit color than ‘Bellise’ (unpatented);        2. ‘Prim 21’ exhibits a fruit ripening time that is 10 days earlier than ‘Grace Star’ (unknown patent protection); and        3. ‘Prim 21’ exhibits a flowering time that is 8 days earlier than ‘Kordia’ (unpatented).        